Download Chapter 2 - Dynamic Cells: Molecules on the Move

Chapter 2 – Membranes and cell
organelles
Life or death for a Cell? (p. 33)

Groups of similar cells form ______________ and groups of tissues come
together to form _______________. The death of cells is a natural feature of
healthy tissue. This ‘programmed cell death’ is called ________________ .

In apoptosis, cells respond to ___________________ which can come from
either inside or outside a cell. Messages from outside the cell bind to cell
death receptors (membrane proteins).

Cell death and cell reproduction are generally balanced in tissues. If this
balance is not regulated, an uncontrolled increase in cells can occur and a
_____________ develops. If a tumour invades healthy tissue, it is said to be
malignant. A malignant tumour is called ______________ .

Too little apoptosis can lead to cancer and too much can cause
degenerative diseases such as Alzheimer’s.
Note: Apoptosis is different to necrosis which is the term used to describe the
death of a cell due to damage caused by mechanical or chemical trauma.
Looking at eukaryotic cells (pg 37)
 Each living cell is a small compartment with an outer boundary, the
_____________________________________
 Cells produce substances that need to be modified and stored in special
compartments.
These
special
compartments
are
called
________________________
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
Within the compartment is a fluid called __________________

Organelles are held in place by a network of fine ________________________
called __________________________

A typical animal cell:. (refer to figure 2.8 on page 39 of text)
Common Misconception:
Human red blood cells ARE eukaryotic even though they don’t possess a nucleus
when mature. These cells did have a nucleus, which was lost, as the cells matured
and became specialized for oxygen transport.

There is no such thing as a typical cell. Cells are specialized. That is they are
designed to carry out a specific function.
E.g.
Nerve cells are specialized for ___________________________
Muscles cells are specialized for _________________________
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

Organelles can be viewed as membrane-bound compartments which are sites
for chemical activity. (only found in eukaryotic cells)
There are some features that are shared by all cells; both prokaryotic &
eukaryotic, as follows:
1. _____________________________________
2. _____________________________________
3. _____________________________________
All cells carry out basic processes in addition to any special function. They;

________________________________________

________________________________________

________________________________________

________________________________________

________________________________________
All these activities require considerable amounts of energy and the production of a
variety of biomolecules. These processes are precisely regulated and catalysed by
enzymes (a type of protein)
There are many factors, which are important for optimal cellular activity such as;






The composition of the extra cellular fluid
Salt concentration
Temperature
Nutrient levels
pH
Removal of wastes
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The Plasma Membrane Boundary (p.39)

All living things are bounded by the plasma membrane, which controls the entry
of dissolved substances into and out of the cell.

The plasma membrane can be seen under an _______________ microscope.

Plasma membranes are ____________________ permeable. It allows some
substances through and not others.

A plasma membrane comprises a ___________________ bilayer into which
proteins and ________________ protrude. Some proteins which are embedded
in this layer form________________ that allow certain substances to pass
across the membrane in ________________ direction.

The is called the ________________________ model (See Fig. 2.9 pg 39)
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
Some cells also have an additional exterior cell wall comprised of
_________________.

All membranes in a cell are made up of a double layer of
____________________ molecules (the phospholipid bilayer).
The phospholipids consist of a hydrophilic head
(_________________________) and a hydrophobic tail
(__________________________).

e.g.

This means that the head dissolves in water whereas the tails are
_____________ and forced to face inwards away from the watery environment.

The lipid structure of the membrane gives it the unique property of being
___________________ and being able to __________________ itself.
The plasma membrane also contains:
(1)
Cholesterol molecules – gives the membrane some rigidity and water
resistance.
(2)
A range of different proteins:
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Type of Protein
Function
Allows some substances, such as ions, to move through
the membrane. There are 2 types of transport proteins:
channel proteins & carrier proteins.
Hormones & other substances bind to them affecting the
cell’s activities. Different types of cells have different
receptor proteins.
e.g.
Act as markers called ‘antigens’ which enable the
immune system to recognize ‘self’ cells from ‘non-self’
cells.
Join cells together in multicellular organisms
Recognising Cells: self or non-self (pg 40)




On the outer surface , a plasma membrane has substances called
______________ that “label” or identify a cell as belonging to one particular
__________________.
Antigens usually consist of proteins combined with ___________________
These antigens differ between __________________. If cells from one
organism were introduced into the body of another organism of the same
species, the _____________ system recognizes these cells as
_______________.
The immune system responds with chemical and cellular attacks which kill
________________ cell.
Crossing the Membrane (Pg 40)
 Plasma membranes are ____________________ permeable. This means
that the plasma membrane allows some dissolved substances through but
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not others. Generally these dissolved substances are in solution, but some
may be ___________________ particles.
Free Passage (pg 40)

______________ is the net movement of a molecule or ion from a region of
high concentration to a region of low concentration. (See Fig. 2.10a pg 41)

It is a passive process therefore does not require energy.

At all times molecules are in _________________ movement.

If substances are _____________ concentrated outside the cell than inside,
molecules move from outside to inside the cell.

Diffusion stops at the stage when the concentration of substance X is
_______________ on both sides of the membrane.

Some substances that can dissolve readily in
____________________ of “water-loving”.

Some substances that have low water solubility or do not dissolve in water
but are able to dissolve in or mix uniformly in lipids are called
__________________ (sometimes called hydrophobic) eg: alcohol, ether.
These substances can readily pass through the membrane.

One special case of diffusion: the process of ________________, occurs
when the net movement of water molecules occurs by diffusion across the
cell membrane.
water are
called
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Channel mediated
 Some substances that are unable to carry out _________________ through
the phospholipid bilayer gain free passage with the assistance of
_____________________
 Molecules move from a region of _____________ concentration to a
____________ concentration without requiring energy
Carrier Mediated
 Sometimes a channel protein alone is insufficient to move a molecule down
the concentration gradient. When a specific carrier molecule is required, this
is also called __________________ diffusion
 Mainly involves substances that cannot move across the membrane by
_____________________
 Eg: the movement of ___________________ across the membrane of a red
blood cell.
 Passive process, therefore ______________ require energy expenditure.
(refer to fig 2.10b and c of text))
HW: Complete Biozone worksheet pg 27-28: Membranes in Cells
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Solutions & cells:

Plasma membranes are permeable to water molecules but selectively
permeable to solutes.

The amount of water in the _________________ environment will affect the
concentration of the solution inside the cell.

If the surrounding fluid is more dilute (lower concentration) that the solution
inside the cell, the external solution is said to be ____________________
(hypo – low) and there will be a net movement of water
__________________ the cell.
e.g.

If the surrounding fluid is more concentrated (higher concentration) than the
solution inside the cell, the external solution is said to be
__________________ (hyper – higher) and there will be a net movement of
water _________________ the cell.
e.g.

When the surrounding fluid is of equal concentration to the solution inside
the cell, the external solution is said to be ___________________ and there
will be no net movement of water (i.e. water will diffuse equally in both
directions).
e.g.
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Cell walls and movement of water molecules

Plant cells contain a freely permeable cell wall and a large vacuole which
contain sap which is rich in _____________, a solution of _____________
concentration.

If the external concentration of water molecules is greater than inside the
vacuole, water will move freely into the vacuole via ____________ from
adjacent cells. The vacuole swells and pushes the cell membrane against
the _________ ___________, making the cell _____________.

This pressure is called ____________ pressure.
e.g.
Note:
The cell wall limits the expansion of the cell membrane; therefore the
cell will not burst.

If the concentration of water in the ____________ environment is less than
the vacuole then water will move __________ via osmosis.

This reduces the size of the vacuole, the plasma membrane moves away
from the cell wall and the cell becomes flaccid (limp).

This process is called _________________.
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e.g.
Paid Passage : ACTIVE TRANSPORT (pg 41)
Active transport is the movement of molecules or ions from a region of
low concentration to a region of high concentration.



Occurs against the concentration gradient and therefore requires energy
(hence ‘active’)
Movement involves carrier proteins
Is extremely important as it allows cells to take up nutrients even when
concentrations outside the cell are very low & to excrete waste
(refer to fig 2.10d text)
Bulk Transport (pg 41)

The process of bulk transport of material into the cell is called
_______________
 Smaller particles (pinocytosis) and larger particles (phagocytosis) are
actively transported into the cell.
 Requires energy.
(refer to fig.2.11a from text)

Bulk transport out of cells (eg: transport of material from
_____________________) is called Exocytosis
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

Large particles are actively transported out of the cell by moving them in
small vacuoles called _______________ .
Requires energy.
(refer to fig 2.11b from text))
FACTORS AFFECTING THE MOVEMENT OF MATERIALS INTO AND OUT OF
CELLS
Two key factors will affect the movement of materials into and out of a cell:
1. Concentration gradient – the larger the concentration gradient the higher the
rate of diffusion.
e.g.
2. Surface area to volume ratio – the larger the SA:VOL the faster and therefore
more efficient the rate of diffusion.
Cells are limited in the size to which they can grow because of this. Larger cells
are often thin & elongated or have increased folding in the cell surface in order
to increase the surface area.
e.g.
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Plants have Cells Walls (pg 42)


Cell walls are found in plants, fungi and bacteria. The composition of the cell wall
differs:
Plants:
________________________
Fungi:
________________________
Bacteria:
peptidoglycan (network of carbohydrates, lipids & amino
acids)
The cell wall is freely permeable which means that it allows a lot of particles to
pass through it.
Cell Organelles
Organelle 1: The Nucleus – Control Center (pg 42)

The nucleus in ________________________ cells forms a distinct spherical
structure enclosed by a ___________________ membrane called the
__________________________.

Cells that lack a distinct nucleus are called _____________________ (eg
________________ from the Kingdom Monera)

Genetic Material is usually dispersed throughout the nucleus, however become
organized into _________________ during cell reproduction.
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Organelle 2: mitochondrion – energy-supplying organelle (pg 44)

Cells use energy in the form of ATP or _______________________________.

ATP is produced during the process of _________________________, and in
Eukaryotic cells this process occurs in the _______________________.

Mitochondria consist of 2 membranes:
- Outer Membrane
- Inner membrane, which is __________________, and is the site of ATP
production

Prokaryotic cells lack mitochondria.
Organelle 3: Ribosomes – protein factories
 Living cells make proteins by linking amino acids into long chains, forming
proteins. Ribosomes are the site of __________________ production.

Ribosomes lack a membrane but can be attached
___________________, or can be found in the _________________
to
the

Proteins
manufactured
by
________________________
to
be

Proteins synthesized by ‘free’ ribosomes are for _______________________
with cell.

Ribosomes
are
composed
of
(___________________________),
_____________________.
Rough
ER
are
destined
__________________
which
comes
and
from
rRNA
the
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Organelle 4 and 5: endoplasmic reticulum and Golgi Complex (pg 46)

Transport of substances within the cell occurs through the system of channels
forming the ___________________________.

Channel walls are formed by ___________________

The Golgi complex is a system of ___________________ membranes which
package substances into ________________for transport outside the cell.
HW: Complete pg 31 “Modification of Protein
pg 32 “Packaging Macromolecules
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Connections between cells: Animal cells (pg 52)

Eukaryotic cells have an internal framework of protein fibres (microtubules,
microfilaments and intermediate filaments). These give strength and support to
the cell and are referred to as the ___________________

These three structures combine to assist in:
i.
__________________________________________________________
ii.
__________________________________________________________
iii.
__________________________________________________________
iv.
__________________________________________________________
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ORGANELLES IN ACTION
Organelle
Nucleus
Refer to pages 42 to 51 and complete the table below. Also see Biozone pg 29-30
Structure
Function
Other features associated with it
Ribosomes
Endoplasmic reticulum
Golgi apparatus
Lysosomes
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Summary:
Process
Packaging & Transport of Macromolecules.
Passive or Active
With or Against
concentration
gradient
Part of cell and/or structures involved in process
Diffusion
Osmosis
Facilitated
diffusion
Active
transport
Exocytosis
Endocytosis
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